(1) Field of the Invention
This invention relates to an auger-type ice making machine and, in particular, to the structure of an upper bearing for rotatably supporting the upper section of the auger.
(2) Description of the Related Art
In an auger-type ice making machine, a refrigeration casing is cooled from the outside to generate ice on the inner surface of the casing. The ice is scraped off by a helical blade and pushed up and out of the casing. FIG. 13 shows a part of a typical conventional auger-type ice making machine. In the drawing, a cylindrical refrigeration casing 1 holds at its upper end a press head 3, which includes an ice compression passage (not shown). The ice which has been scraped off is compressed as it is led upward through this compression passage. The press head 3 supports an upper shaft section 7b of an auger 7 through the intermediation of a slide bearing 5.
As can be seen from FIG. 13, the auger 7 includes a helical blade 7a, which scrapes off ice and feeds it upwards, thereby receiving a downwardly directed resistance force. The press head 3, which is pressed by the ice being scraped off and fed upwards, receives an upwardly directed force. Due to these downwardly and upwardly directed resistance forces, the gap between the lower end surface 3a of the press head 3 and the shoulder surface 7d of the auger 7 tends to become enlarged. Further, when the ice making water freezes, impurities in the water, such as silica and calcium, have a tendency to move to the unfrozen portions of the water, resulting in increased concentrations near the lower end of the press head 3, where these impurities are likely to be deposited. These deposited impurities in the form of fine solid particles are easily forced into the slide bearing 5 through the enlarged gap. It goes without saying that infiltration by solid impurities into the bearing surface is likely to cause damage to the bearing.
The ice pushed out of the casing 1, after passing upwards through the ice compression passage, is cut to a predetermined size by a cutter 9 attached to the upper end of the auger 7. Thus, the upper shaft section 7b of the auger 7 receives a reaction force when the ice is cut, so that the bearing section is subject to great frictional force. Thus, the bearing section of the upper shaft section 7b of the auger 7 is in a severe environment in terms of the load applied thereto as well as from the matter deposited on the bearing surface.
In view of the above, various proposals have been made for the purpose of protecting the upper bearing section of an auger-type ice making machine from damage. According to one such proposal, a thrust bearing is provided at the upper end of the upper shaft section to thereby transmit the downwardly directed force of the auger to the press head. Further, a radial bearing is provided at the lower end of the upper shaft section to thereby receive any torque reaction. Due to this arrangement, the auger and the press head are integrated, so as to prevent the generation of a gap therebetween. Further, the two bearings are surrounded by two oil seals, thereby preventing the penetration of water and impurities and the leakage of lubricant (See Japanese Patent Laid-Open No. 58-21020).
According to another proposal, a plurality of grooves are provided on both the upper shaft section of the auger and the lower section of the press head, which is placed above the helical blade to correspond thereto. In these grooves, sherbet-like ice, which would otherwise penetrate the bearing section as a result of being pressurized in the compression passage, is solidified, thereby preventing the penetration of ice or other foreign matter into the bearing section (See Japanese Utility Model Laid-Open No. 60-187887).
According to a third proposal, a recess is formed in the lower section of the press head or in the upper end surface of the helical blade of the auger, and a sliding member is provided in this recess, thereby preventing abnormal wear of the press head and the auger, which are made of the same material (See Japanese Utility Model Publication No. 61-32304).
Further, in accordance with a fourth proposal, the rib forming the ice compression passage of the press head protrudes downwards from the boss section, and a washer for adjusting the gap between the rib and the auger upper surface is provided in the recess, thereby preventing both clogging by ice and the radial displacement of the auger (See Japanese Utility Model Publication No. 3-36858).
In accordance with the first proposal, the press head and the auger are integrated to keep the dimension of the gap therebetween constant. However, when particles of sherbet-like ice or foreign matter in the water are pressed against the lip of the lower oil seal, the lip is liable to suffer damage, resulting in a reduction of the service life of the bearing due to water penetration, lubricant leakage, etc. Thus, this proposal cannot easily be put into practical use. In the second proposal, the sherbet-like ice infiltrating the grooves is solidfied to prevent foreign matter in the water from penetrating the bearing section. This effect, however, cannot be obtained in the early stages of operation. As to the third and fourth proposals, in which the case of a washer or the like is adopted, the gap has a tendency to expand, as described above, due to the directions in which forces are applied, so that the expected effect can not be attained.
Thus, each of these proposals has its merits and demerits, which means none of them completely solve the problems of the prior art.